In general, devices are known for the continuous production of foam blocks having a rectangular cross-section. These known devices comprise an endless conveyor belt with side walls wherein the carrying run of the conveyor belt and the side walls are adapted to be covered with a film, a distributing device for a foamable reaction mixture which is located over the inlet end of the conveyor belt, and a plurality of mold covers which are placed along the foaming area and fixed to guiding mechanisms.
The mold covers provide for an even surface of the nascent foam block. They must be adaptable to the height of the reacting reaction mixture or of the foam which is being formed, without the bearing pressure being altered. This necessarily means that the position of the mold covers must vary with variations in the height of the surface of the foam block which is being formed, which usually results in a variation of the angle of pitch or a displacement in the foaming area.
A device has therefore been proposed in which the mold covers are hung on pivotal levers and the bearing pressure is controllable by means of counterbalances. At the beginning and end of the foaming process, and during variation in the height of the foam during production, the mold covers experience, in addition to vertical movement, a movement in or opposite to the conveying direction of the conveyor belt. It has been found that this movement may be as much as 600 mm or more. Thus a disadvantageous pushing or pulling force component is exerted on the surface of the foam which may cause compression and cracks.
In other known devices, the mold covers are held in guiding mechanisms by means of vertical rods. The bearing pressure is controlled by adjustable springs or by counter-balances. These devices have proved particularly disadvantageous, since during adjustment in height, friction in the guiding mechanisms of the rods causes an appreciable hysteresis of the bearing forces. Considering the low bearing force, of from 2 to 6 mbar, required for the mold covers on the foam which is being formed, this phenomenon is undesirable.
Characteristic of these devices are those disclosed in U.S. Pat. No. 3,984,195.
An object of the invention is to provide a device in which the mold covers may reciprocate in a direction which is as vertical as possible and be free of interfering forces.